The present invention relates to an ink jet printing apparatus for providing ink images with a protection film.
Ink jet printing has become a prominent contender in the digital output arena because of its non-impact, low-noise characteristics, and its compatibility with plain paper. Ink jet printing avoids the complications of toner transfers and fixing as in electrophotography, and the pressure contact at the printing interface as in thermal resistive printing technologies. Ink jet printing mechanisms include continuous ink jet or drop-on-demand ink jet. U.S. Pat. No. 3,946,398, which issued to Kyser et al. in 1970, discloses a drop-on-demand ink jet printer which applies a high voltage to a piezoelectric crystal, causing the crystal to bend, applying pressure on an ink reservoir and jetting drops on demand. Piezoelectric ink jet printers can also utilize piezoelectric crystals in push mode, shear mode, and squeeze mode. EP 827 833 A2 and WO 98/08687 disclose a piezoelectric ink jet print head apparatus with reduced crosstalk between channels, improved ink protection, and capability of ejecting variable ink drop size.
U.S. Pat. No. 4,723,129, issued to Endo et al, discloses an electrothermal drop-on-demand ink jet printer which applies a power pulse to an electrothermal heater which is in thermal contact with water based ink in a nozzle. The heat from the electrothermal heater produces a vapor bubble in the ink, which causes an ink drop to be ejected from a small aperture along the edge of the heater substrate. This technology is known as Bubblejet(trademark) (trademark of Canon K.K. of Japan).
U.S. Pat. No. 5,635,969 discloses a print head that conditions the ink receiver by ejecting a treatment fluid to the receiver before printing of the ink image on the receiver. The treatment fluid on the receiver helps to immobilize the ink pixels that are later printed on the receiver, which improves dot shape and thereby improving the quality and stability of the print.
Ink jet images often have problems associated with image durabilities. Image durability can include durability against physical abrasion, stability against water (i.e. water fastness), light fade (i.e. light fastness) and environmental conditions (oxidation etc.), and contamination such as fingerprints on the image. A traditional method for enhancing durability of ink jet images is to bond a lamination sheet on the ink image using a lamination machine. The lamination sheet is pre-coated with an adhesive layer. Pressure and heat are usually required to bond the lamination and the ink receiver together.
Several drawbacks exist with the lamination method. First, the lamination sheet significantly increases the cost of the media per unit area. Second, the lamination machine is expensive, sometimes more costly than the ink jet printer itself. Third, the lamination has the tendency to de-laminate over time or under physical or heat disturbance.
An object of this invention is to provide ink jet printing apparatus which produce ink images on receivers with enhanced image durability.
This object is achieved by apparatus for forming durable ink image in response to a digital image on a receiver, comprising:
a) at least one ink jet print head adapted to deliver ink to the receiver;
b) means for actuating the ink jet print head for delivering ink to the receiver to form an ink image in accordance with the digital image; and
c) fluid ejection means for applying a fluid over the ink image which forms a transparent solid continuous film for protecting the ink image.
An advantage of the present invention is that a polymer protection film can be formed effectively with apparatus in accordance with the present invention with significantly reduced material and equipment costs.
Another advantage of the present invention is that lamination and associated drawbacks can be eliminated by forming a polymer protection film in accordance with the present invention.
Yet another advantage of the present invention is that the thickness and the area of the polymer protection film can be controlled by a computer and control electronics.
A feature of the present invention is that a polymer protection film is applied using an ink jet print head as a post-print step.
A further advantage of the present invention is that the application of the polymer overcoat film does not involve the contact of an applicator with the ink image, which reduces the probability of disturbing the ink images.